Sex therapists are aware of the issues that you are raising. They routinely work with individuals and couples who are trying to recover from affairs.

To say that a person should never be with someone who cheated is a valid perspective and I respect that. Here, however, OP evidently does not share that perspective. In fact, she says that things are "great" except for sex. For better or worse, she is seeking help with sex, not with leaving her husband. A sex therapist is therefore a good choice for her. A sex therapist would not be a good choice for everyone.